What silver nitrate is
Silver nitrate is the silver(I) salt of nitric acid, AgNO3. It is a versatile precursor to many other silver compounds, including the silver halides used in photography. It forms colourless or white crystals with no odour, and it turns grey to black when exposed to light or organic material. It is also known as lunar caustic.
| Item | Entry |
|---|---|
| Chemical formula | AgNO3 |
| Molar mass | 169.87 g/mol |
| CAS number | 7761-88-8 |
| EC number | 231-853-9 |
| Other name | Lunar caustic |
| UN number | 1493 (oxidizing substance, Class 5.1) |
| HS code | 2843.21 |
Key properties
The values below come from PubChem (compound 24470, which collects the US Hazardous Substances Data Bank) and the ILO/WHO International Chemical Safety Card 1116.
| Property | Value |
|---|---|
| Appearance | Colourless or white crystals, odourless; turn grey on exposure to light |
| Melting point | 212 °C |
| Decomposition | About 440–444 °C, giving silver metal, oxygen and nitrogen oxides |
| Density | 4.35 g/cm³ at 20 °C |
| Solubility in water | Very soluble: 122 g in 100 mL at 0 °C; 245 g per 100 g of water |
| Other solvents | 1 g dissolves in about 30 mL of ethanol or 253 mL of acetone; readily soluble in ammonia water; soluble in glycerol |
| Stability | Light sensitive; with a trace of nitric acid present it is stable up to 350 °C |
Two points matter in practice. First, silver nitrate is very soluble in water, so it is usually supplied as crystals and made up into solution by the user. Second, it is light sensitive: on exposure to light in the presence of organic matter it darkens, which is why it is stored in light-proof containers and why it leaves dark stains on skin and fabric.
How it is made
Silver nitrate is made by dissolving silver metal in nitric acid. With dilute acid the reaction is:
3 Ag + 4 HNO3 → 3 AgNO3 + NO + 2 H2O
The process described in the Hazardous Substances Data Bank then evaporates the solution, heats the residue to a dull red heat to break down any copper nitrate (copper is a common impurity in silver), dissolves the residue in water, filters it and recrystallises the silver nitrate.
What it is used for
PubChem lists a wide range of uses for silver nitrate. The main ones:
| Use | What silver nitrate does |
|---|---|
| Chemical analysis | Reagent for chloride and other halides; described in the data bank as a very important and extensively used analytical reagent |
| Other silver compounds | Starting material for silver halides (silver bromide and silver chloride) and other silver salts |
| Mirrors and silvering | Source of silver for mirror manufacture and silver plating |
| Photography | Used in photography and photographic processing, mainly through the silver halides made from it |
| Inks and dyes | Indelible and sympathetic inks, hair dyes, colouring porcelain |
| Catalysts and synthesis | Used as a catalyst; in organic synthesis it is used to remove (abstract) halide ions |
| Laboratory staining | Silver staining of proteins and nucleic acids in gels, and sample preparation for electron microscopy |
| Medicine | A local anti-infective; dilute solutions (0.5%) have been used in the treatment of extensive burns, and it is used to cauterise tissue |
Medical and pharmaceutical uses require a pharmacopoeial grade and are regulated product by product, so they are outside the scope of an industrial chemical supply.
Silver nitrate in chemical analysis
Silver ions react with chloride, bromide and iodide to form silver halides that are almost insoluble in water. That reaction is the basis of two everyday laboratory uses:
- Chloride test: a few drops of silver nitrate solution added to a sample acidified with nitric acid give a white precipitate of silver chloride if chloride is present.
- Argentometric titration: a standard silver nitrate solution is used to measure chloride in water, brines and many products. In the Mohr method, potassium chromate is the indicator; once all the chloride has precipitated, the first excess of silver forms red-brown silver chromate, which marks the end point.
For this work the reagent grade matters: chloride and other halide impurities in the silver nitrate itself, and the purity of the water used to make the solution, both affect the result. Standard solutions are kept in brown bottles because of the light sensitivity.
Grades
Silver nitrate is sold mainly as a technical (industrial) grade for silvering, plating and chemical manufacture, and as an analytical reagent (AR or ACS) grade for laboratories. Pharmacopoeial grades exist for medicinal products. The grades differ in assay and in the limits on impurities. A Certificate of Analysis for silver nitrate typically reports:
- Assay as AgNO3
- Appearance and clarity of the solution
- Insoluble matter
- Chloride and sulphate
- Heavy metals and specific metals such as copper, iron and lead
Always compare the certificate with the specification your process or method needs rather than relying on the grade name alone.
Hazards and safe handling
Silver nitrate carries the signal word Danger. Its International Chemical Safety Card gives the EU classification H272 (may intensify fire; oxidiser), H314 (causes severe skin burns and eye damage), H400 and H410 (very toxic to aquatic life, with long-lasting effects); under the UN GHS criteria the card also lists it as a strong oxidiser that may cause fire or explosion and as harmful if swallowed. The card adds:
- Strong oxidant: not combustible itself, but it enhances the burning of other materials and reacts violently with combustible substances, reducing agents, acids, acetylene and many other substances.
- Corrosive: corrosive to the eyes, skin and respiratory tract. It may also affect the blood (methaemoglobin formation), and repeated exposure can cause argyria, a grey-blue discolouration of the skin and eyes.
- Exposure limit: the ACGIH TLV is 0.01 mg/m³ as silver (8-hour time-weighted average).
- Protection: gloves, protective clothing, a face shield or eye protection, and local exhaust to avoid inhaling dust.
- Storage: keep it separate from combustible materials and reducing agents, in well-closed original containers, protected from light, in an area without drain or sewer access.
- Spills: sweep into covered, sealable containers; do not absorb it in sawdust or other combustible absorbents, and do not let it enter the environment.
Rinse contaminated clothing with plenty of water, because clothing soaked with an oxidiser is a fire risk.
Transport and the HS code
Silver nitrate ships as UN 1493, Silver nitrate, hazard Class 5.1 (oxidizing substance), Packing Group II, according to the ICSC. The US hazardous materials table lists the same entry with a 5.1 label, and the Emergency Response Guidebook (2024) assigns it Guide 140 for oxidizers, which advises water for small fires rather than dry chemical or foam.
For customs, silver nitrate has its own subheading: HS 2843.21. In the US tariff the line is 2843.21.00.00, with a general duty rate of 3.7%.
Questions to ask a supplier
- Which grade is it: technical, analytical reagent (AR/ACS) or pharmacopoeial?
- What assay is guaranteed, and does the Certificate of Analysis cover chloride, sulphate, insoluble matter and metals such as copper, iron and lead?
- Is it supplied as crystals or powder, and in light-proof inner packing?
- Is the outer packaging approved for UN 1493, Class 5.1, Packing Group II, and will a 16-section Safety Data Sheet come with the shipment?
- What are the lot number, date of manufacture and recommended shelf life?
- How will the packages be kept away from combustible cargo in transit?
Enquire with Scapex Exports
Scapex Exports is an exporter and supplier of inorganic and laboratory chemicals from India. Our silver nitrate (technical) and silver nitrate AR pages list the grades, packing and documents. For argentometric work we also supply potassium chromate, and nitric acid 68% is covered in our guide to nitric acid. Our sodium chloride guide covers the salt most often measured with silver nitrate.
Tell us the grade, quantity, packing and destination port, and we will reply with a quotation.
Frequently asked questions
What is the chemical formula of silver nitrate?
AgNO3. Its molar mass is 169.87 g/mol and its CAS number is 7761-88-8. It is the silver(I) salt of nitric acid.
Why does silver nitrate turn black and stain skin?
Silver nitrate is light sensitive. On exposure to light in the presence of organic matter, such as skin, it turns grey to black, which is why spills leave dark stains. It should be stored in light-proof containers.
Is silver nitrate soluble in water?
Yes, very. About 122 g dissolves in 100 mL of water at 0 °C, and the solubility rises sharply with temperature. It also dissolves in ethanol, glycerol and ammonia water.
Is silver nitrate dangerous goods for shipping?
Yes. It ships as UN 1493, Class 5.1 oxidizing substance, Packing Group II. It is corrosive and very toxic to aquatic life, so it needs approved packaging, hazard labels and a Safety Data Sheet.
What is the HS code for silver nitrate?
HS 2843.21, a subheading that covers silver nitrate only. The US tariff line is 2843.21.00.00.
Sources: PubChem, Silver nitrate, CID 24470 (including Hazardous Substances Data Bank records); ILO/WHO International Chemical Safety Card ICSC 1116, Silver nitrate (April 2024); NOAA CAMEO Chemicals, UN/NA 1493 with Emergency Response Guidebook 2024, Guide 140; US Harmonized Tariff Schedule, subheading 2843.21.00.00.